1. Field of the Invention
This invention relates to chemical mechanical polishing. More specifically, the present invention provides a conditioner assembly and conditioner back support for a chemical mechanical polishing apparatus. Moreover, the present invention provides a method for conditioning a polishing pad of a chemical mechanical polishing apparatus by employing the conditioner assembly and the conditioner back support of the present invention.
2. Discussion of the Background
Sub-micron integrated circuit devices are formed on substrates such as semiconductor wafers by patterning conductive or interconnect film layers (e.g., aluminum (Al), copper (Cu), etc.) which have been deposited on nonconductive or intermediate dielectric film layers (e.g., silicon oxide (SiO.sub.x)). In order to pattern or etch the interconnect film layer, the exposed surface of the interconnect film layer must be topographically planar. An intermediate dielectric film layer having a non-planar surface will transfer its topographical profile to that of the deposited interconnect film layer. As a result, prior to the deposition of the interconnect film layer, the surface of the intermediate dielectric layer has to be planarized. To pose the problem more concretely, the patterning and etching step is prepared by selectively developing photoresist layers on the exposed surface of the interconnect film layer. A non-planar surface prevents the focusing of a photolithography apparatus on the entire exposed surface of the interconnect film layer for the exposure of the photoresists. As a result, the interconnect film layer having a surface defined by a non-planar topography cannot be etched or patterned by photolithographic techniques. The syllogism follows that the intermediate dielectric film layer, on which the interconnect film layer is deposited, must have a planarized surface.
Chemical mechanical polishing (CMP) is one recognized method of planarization. CMP technique requires that the substrate be mounted on a polishing head with the surface of the substrate to be polished exposed. The polishing head, supporting the substrate, is then placed against a polishing pad of a linear polishing belt or a planar polishing pad. Referring to FIGS. 50 and 51, which are schematic side elevational and front plan views of a linear CMP apparatus, generally illustrated as 300, there is seen a continuous, vertical polishing belt 302 configured to polish a vertically held substrate, such as a semiconductor wafer 305. A polishing head 301 positions the substrate 305 against a polishing pad 304, which is attached to the vertical polishing belt 302. The polishing belt 302 is kept in continuous motion, as indicated by arrow 308, by rotating pulleys 310 and 312 at a selected polishing speed (e.g., 1-10 meters/second). A support head 314 provides a base for the application of pressure (e.g., 1-10 PSI) by the polishing head 301 against the substrate 305. The polishing head 301 rotates in a clockwise or counter-clockwise direction, as indicated by arrow 316, and is oscillated back and forth, as indicated by arrow 320, by an oscillating arm 318 of a driving mechanism (omitted from the Figures). Moreover, a slurry, typically a mixture of an abrasive and at least one chemically reactive agent, is supplied to the polishing pad 304. Accordingly, a chemical reaction and a mechanical abrasion is provided at an interface between the substrate 305 and the polishing pad 304.
A planar CMP apparatus 400, as illustrated in FIGS. 52 and 53 includes the polishing head 301, horizontally supporting the substrate 305. The polishing head 301, as mentioned above, rotates in a clockwise or counterclockwise direction, as indicated by the arrow 316, and is oscillated back and forth, as indicated by the arrow 320, by the oscillating arm 318 of the driving mechanism (omitted from the Figures). However, in lieu of the continuous, vertical polishing belt 302, a rotating, planar polishing platen 402 is provided. The planar polishing platen 402 supports and rotates the polishing pad 304 about a driving shaft 406. The rotation of the polishing platen 402 is indicated by arrow 408. The slurry is provided to the polishing pad 304 for providing the abrasive chemical solution.
The various motions of the different components of the above-discussed linear 300 and planar 400 CMP apparatus often lead to excessive wear near the center of the polishing pad 304 and less wear in the periphery. Consequently, non-uniformity is introduced through the polishing pad 304 into the intermediate dielectric film layer. To maintain uniformity in the polishing of the exposed surface of the intermediate dielectric film layer and to provide reproducibility of the polishing process, the polishing pad 304, which is typically a polyurethane pad, is required to be conditioned between or during use. Conditioning is necessary to maintain the uniformity of the polishing pad's 304 texture and profile.